I must be bored :-) Your question tickled a nerve somewhere and I decided to do some research. Several hours and countless websites later, I know more than I thought I ever wanted to about hybrid (??.....or maybe not) camellias.

Without going into an entire dissertation, this is what I learned:

There appears to be a lot of taxonomic confusion. Depending on source, both C. hiemalis and C. vernalis are reported to be C. japonica x sasanqua hybrids that occurred naturally back in the mists of time to the point where they may or may not now be considered distinct species. Some sources list one but not the other as valid species and/or hybrids. And I could not find any definitive explanation as what the difference was between the two. Both are intermediate in morphology and bloom time than the two parent species, although vernalis is reported to more closely resemble the sasanqua parentage and hiemalis the japonica parentage.

Even Nuccio's, who is credited in bringing the cultivar 'Egao' to the US from Japan in the late 70's, is a bit confused about this plant and refers to it as a sasanqua.

The term 'Egao Group' came up more than once (together with 'Gaisen Group'), implying that current cultivars are mostly sports of these two very old hybrids (each with opposing pollen parents). And apparently these cultivars, like Corkscrew Egao or Shibori-Egao, are more popular or more active in commerce than the original 'Egao' as there is much more info available on them. And many more sources.

Here is a link to a photo of Egao from the ICS database: https://internationalcamellia.org/international-camellia-register?camelliaId=5461&state=b

And since you are in the Bay area, you might want to seek out Yuri Panchul in Sunnyvale. He is a noted camellia hybridizer and his websites, http://camellia-sasanqua.com and http://sazanka.org, provided some of the best info I could find on this plant.

btw, care instructions for Egao would be no different than any sasanqua or xvernalis cultivar.

I have not seen any special care instructions on Egaos either but post if you find any. They tend to have leaves that are slightly more Japonica like in size so I treated one as a japonica and put it in afternoon/evening shade. The blooms tended to drop intact, instead of sometimes falling down in pieces, which was nice since I like to pick them up to minimize the chances of ever getting camellia petal blight in my camellias. The plant did have a tendency to look thick on the inside, which led me to move my watering time closer to sunrise when I was still using a sprinkler. I have moved since but I wonder if the plant is still alive.

@gardengal48 Thank you for your extensive research. You confirmed for me that this is a variety that is not well documented, unless you are willing to pull together pieces from many places, as you did.